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Percentage Unchanged

If the base of a rectangle is increased by 10% and the area is unchanged, by what percentage (exactly) is the width decreased by ?

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Circle Packing

Equal circles can be arranged so that each circle touches four or six others. What percentage of the plane is covered by circles in each packing pattern? ...

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Round and Round

Prove that the shaded area of the semicircle is equal to the area of the inner circle.

Antiques Roadshow

Stage: 4 Short Challenge Level: Challenge Level:1

The price increased by 30,000 times the original amount, so the profit was 29,999 times the original amount, which is a 2,999,900% profit!

This problem is taken from the UKMT Mathematical Challenges.
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